Make sure QGraphicsScene::update() only requires one event-loop

iteration before the views are updated.

A full scene update (scene.update()) already supported it because the
scene called update() on the views directly. However, partially scene
updates (scene.update(rect)) required two event-loop iterations
before the views were updated.

Auto-test included.

1 files changed, 27 insertions, 0 deletions

diff --git a/tests/auto/qgraphicsscene/tst_qgraphicsscene.cpp b/tests/auto/qgraphicsscene/tst_qgraphicsscene.cpp
index e9d6f1d..f7ea4ce 100644
--- a/tests/auto/qgraphicsscene/tst_qgraphicsscene.cpp
+++ b/tests/auto/qgraphicsscene/tst_qgraphicsscene.cpp
@@ -236,6 +236,7 @@ private slots:
     void contextMenuEvent();
     void contextMenuEvent_ItemIgnoresTransformations();
     void update();
+    void update2();
     void views();
     void event();
     void eventsToDisabledItems();
@@ -2779,6 +2780,32 @@ void tst_QGraphicsScene::update()
     QCOMPARE(region, QRectF(-100, -100, 200, 200));
 }
 
+void tst_QGraphicsScene::update2()
+{
+    QGraphicsScene scene;
+    scene.setSceneRect(-200, -200, 200, 200);
+    CustomView view;
+    view.setScene(&scene);
+    view.show();
+#ifdef Q_WS_X11
+    qt_x11_wait_for_window_manager(&view);
+#endif
+    QTest::qWait(250);
+    view.repaints = 0;
+
+    // Make sure QGraphicsScene::update only requires one event-loop iteration
+    // before the view is updated.
+    scene.update();
+    qApp->processEvents();
+    QCOMPARE(view.repaints, 1);
+    view.repaints = 0;
+
+    // The same for partial scene updates.
+    scene.update(QRectF(-100, -100, 100, 100));
+    qApp->processEvents();
+    QCOMPARE(view.repaints, 1);
+}
+
 void tst_QGraphicsScene::views()
 {
     QGraphicsScene scene;